Membrane container construction for storing low-temperature liquified gas

ABSTRACT

A container or carrier for storing a low-temperature liquified gas in which a thin, metallic, film or membrane fluid-containing inner vessel composed of a bottom wall, side walls and a top having a central opening has a flexible bulge developed on the top in the area of juncture of the top and side walls and this bulge straightens in cross section for compensating for temperature decreases and loading for the inner vessel with a liquified gas. The internal pressure of the inner vessel is supported by a rigid, outer vessel in which a heat-insulating layer of compression-resistant material is installed. The strength of the inner vessel is maintained by the compensating deformations and at the same time leakage of liquid is prevented. Pipes lead into the inner vessel through a trunk mounted on a top wall structure of the outer vessel.

United States Patent Yamamoto et al.

[4 1 May 30, 1972 [72] Inventors: Katsuro Yamamoto, Tokyo; Shinji Nakagawa, Yokohama, both of Japan Bridgestone Liquified Gas Company Limited, Chuo-ku, Tokyo, Japan [22] Filed: Jan. 4, 1971 [21] Appl. No.: 103,740

[73] Assignee:

[30] Foreign Application Priority Data Jan. 14, 1970 Japan ..45/3706 [52] US. Cl ..220/9 LG [51 Int. Cl ..B65d 25/18 [58] Field of Search ..220/9 LG, 9 F, 10; 114/74 A [5 6] References Cited UNITED STATES PATENTS 3,052,203 9/1962 Henry ..220/9 LG 3,150,794 9/1964 Schlumberger ..220/9 LG 3,319,430 5/1967 Small 3,570,701 3/1971 Yamamoto ..220/10 Primary ExaminerAllen N. Knowles AttorneyRobert E. Burns and Emmanuel J Lobato [57] ABSTRACT A container or carrier for storing a low-temperature liquified gas in which a thin, metallic, film or membrane fluid-containing inner vessel composed of a bottom wall, side walls and a top having a central opening has a flexible bulge developed on the top in the area of juncture of the top and side walls and this bulge straightcns in cross section for compensating for temperature decreases and loading for the inner vessel with a liquified gas. The internal pressure of the inner vessel is supported by a rigid, outer vessel in which a heat-insulating layer of compression-resistant material is installed. The strength of the inner vessel is maintained by the compensating deformations and at the same time leakage of liquid is prevented. Pipes lead into the inner vessel through a trunk mounted on a top wall structure of the outer vessel.

4 Claims, 1 Drawing Figure MEMBRANE CONTAINER CONSTRUCTION FOR STORING LOW-TEMPERATURE LIQUIFIED GAS BACKGROUND OF THE INVENTION This invention relates to storing of low temperature liquified gases obtained by liquifying substances which are gaseous at ordinary temperatures such as methane, oxygen and ammonia, by cooling them to their boiling point at ordinary pressure, and more particularly to a membrane receptacle tank construction for storing low temperature liquified gas.

DESCRIPTION OF PRIOR ART Low temperature tank constructions are known in which a heat insulating layer is provided inside a pressure-resisting outer shell and an inner container or vessel is held close to the inner surface of the heat insulating layer. The inner vessel is made of a thin metallic or membrane material plate so that it is flexible, and can be kept in tight contact with the inner surface of the insulating layer. When the inner vessel is subjected to an internal pressure it transmits its internal pressure through the heat insulating layer to the outer shell structure or vessel.

In this type of known storage tank attempts have been made to work out some methods, such as suspending or lifting the top wall of the inner vessel of overcoming the tendency of the inner vessel to sag due to its own weight. The inner vessel undergoes different phases of complicated deformations during the course of change from a unloaded condition at normal temperatures to a loaded condition at low temperatures. The different loading conditions at normal and low temperatures create unfavorable problems of stress concentrations should the inner vessel be provided with any restraints which prevent occurrence of the deformations.

SUMMARY OF THE INVENTION This invention provides a solution to the problems encountered in the known storage tanks of this type which have hitherto been in use. The invention provides a membrane type storage tank or container for low temperature liquified gas which can avoid the irregular sagging of the top wall or structure of the inner vessel due to its own weight. The inner tank has an open top with a boundary portion about its center top opening fixed to the rigid outer shell top structure about the periphery of a rigid trunk on the top structure of the outer tank. By keeping the top wall pressed downwardly in advance at normal temperatures and by connecting the edge or border of the top wall to the side walls of the inner vessel through flexible corners which heave at normal temperatures as in a convex formation, and which can at the same time allow the inner vessel to meet expansion or contraction with no restrictions inside the compression-resisting heat-insulating layer problems of conventional membrane storage tanks are avoided. The membrane vessel according to the invention is made up of side walls and a bottom wall of membrane construction. The inner vessel has a top wall of membrane construction which is open and is connected to the side walls of the membrane tank by a flexible outwardly curved peripheral portion in the area of juncture between the top wall and side walls. This flexible portion, which is convex in vertical cross section, swells upwardly at ordinary temperatures. A rigid outer shell is provided outside the inner vessel with a compression resisting heat insulating layer in between the inner and outer vessels. A rigid trunk is provided on the rigid shell and is positioned at almost the center of the top wall of said inner vessel to which it is fixed to said outer shell, but insulated therefrom through heat-insulating material. The invention is characterized by a feature that the top of the inner vessel is pressed down and deformed or bulged peripherally beforehand at ordinary temperatures by the rigid outer shell or vessel through the heat-insulating layer material which is in contact with the upper surface of the inner vessel top wall.

According to the invention the inner vessel can fully withstand the oscillation which it may undergo when the principles of the invention are applied to the storage tanks of tankers or ships, since the whole of the inner vessel is prevented from crushing and its upper part from sagging, because its side walls of membrane construction are supported by the rigid trunk by way of the flexible curved portion which swells or bulges upwardly. The top wall which has been pressed down beforehand even in an ordinary temperature unloaded condition receives no internal pressure but also is in an expanded condition. The concentration of stresses is avoided because the walls of the inner vessel are allowed to make any thermal deformation freely centering around a portion which is fixed to the rigid trunk at almost the center of the top wall of the inner vessel. Moreover, the walls of the inner vessel will be supported for a sufficiently large area by the compression-resistant heat-insulating layer which is in close contact therewith. Only with the straightening in cross section of or reduction in the bulging of the flexible curved portion and the preliminary pressing-down of the top wall resulted from the thermal contraction of the walls of the inner vessel, in a low temperture loading conditon.

BRIEF DESCRIPTION OF THE DRAWING The illustrated embodiment of the invention is a fragmentary vertical cross section view of a container in accordance with the principles of the instant invention.

Other objects and advantages of the container or receptacle will appear from the following description of an example of the invention; and the novel features will be particularly pointed out in the appended claims.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The drawing is a fragmentary, vertical cross-section view of a container according to the invention and consisting of a double hull acting as a rigid outer shell in which is disposed an inner vessel 3 made of a low-temperature resisting material, such as nickel-steel sheet, stainless steel sheet or aluminum sheet. A heat-insulating layer 2 made of a material having a compression resisting property, such as a hard foamed polyurethane in between, is provided in the interior of the outer shell or vessel between it and the inner tank or vessel 3.

The inner vessel 3 has a side wall 3a and a bottom wall 3b of membrane construction as well as a top wall 3d of membrane construction which is connected to the side wall 3a by way of a flexible portion 36 which swells or bulges upwardly at ordinary temperatures. The top wall is pressed downwardly at ordinary temperature by the outer vessel through a heat-insulating layer 2d which is in contact with its upper surface. That is, the top wall of the inner vessel which was in the condition shown in the drawing by a double-dotted-dash line 3p in the manufacturing of the invention is deformed into a condition illustrated at 3d shown by double solid lines when preliminarily pressed by the heat insulating layer provided in close contact with its upper surface, thereby giving rise to a bulge or upward convex deformation in a flexible curved portion corresponding to a peripheral, marginal portion in the area of juncture of the top wall and side wall. The bulge is received in an annular recess in the heat-insulating layer 2d as illustrated.

At substantially the center of the top wall 3d of the inner vessel, a lower flange or collar of a rigid trunk 5, reinforced by a bracket 4 is fixed the outer shell in a gas tight manner. Upper and lower collars on the rigid trunk 5 are firmly fixed to the double hull serving as the outer shell through mounts 6 and 7 made of a heat-insulating material.

Additional heat-insulating material 8 is provided between the hull 1 and the trunk 5 so that the coldness within the inner vessel cannot exercise a direct effect upon the hull. All the pipes, including the delivery and gas pipes, are admitted into the inner vessel 3 through the trunk 5, and an opening in the trunk 5 is covered by a gas-tight cover, not shown, which is pierced with the pipes or conduits.

When the low temperature liquified gas is introduced, the inner vessel, which is in a condition shown in solid lines in an ordinary temperature unloaded condition, is deformed without stresses into a configuration or condition illustrated at 3Q by a broken line. The thermal contraction, in a loaded condition, centers around a border portion fixed to the trunk 5 and the reduction in or straightening in cross section of the upward bulge or curved portion 30. The walls of the inner vessel, with an exception of the curved portion 30 at its upper, are brought into close contact, by internal pressure, with the compression-resisting heat insultating layer 2, and are supported by the hull l with the heat insulating layer 2 in between the two vessels or receptacles.

While the inner vessel 3 is supported in a stabilized condition in a low temperature loaded conditon where internal pressure acts upon it, the inner vessel 3 of this device can maintain its shape without crushing even in an ordinary temperature unloaded condition in which it receives no internal pressure and is in an expanded condition by virtue of the preliminary pressing of the top wall 3d of the inner vessel and the upward swelling or bulging in the flexible curved portion 30 as well as the partial fixing of the top wall of the inner vessel to the hull 1 through the rigid trunk 5.

According to the invention, as mentioned above, the inner vessel can freely make any thermal distortion or deformation centering around the fixed portion of its top wall, being thereby able not only to prevent the concentration of stresses but also to maintain its shape without difficulty even in an ordinary temperature unloaded condition. The problems encountered in known membrane tanks and containers are avoided because the inner vessel of membrane construction consisting of a top wall which is properly pressed and deformed preliminarily at ordinary temperatures by the outer shell through a compression-resisting, heat-insulating layer, side walls which are connected to said top wall by way of a flexible curved portion which swells upwardly at ordinary temperature, and a bottom wall is supported within the outer shell and the central portion of said top wall alone is fixed to the outer shell through a rigid trunk.

The above description of the invention is that of a carrier, for example a tank on a ship, but the structure described and illustrated may be made as a stationary tank or container. In such a case a foundation, not shown, may be provided under the outer shell for securing it to the ground.

It should be understood, of course, that the foregoing disclosure relates to only preferred embodiments of the invention and that numerous modifications or alterations may be made therein without departing from the spirit and the scope of the invention.

What we claim and desire to secure by letters patent is:

l. A receptacle for storing low-temperature liquified gas comprising, a rigid vessel having a bottom, side walls and top structure, a heat-insulating layer in said vessel, a flexible, inner, fluid-containing vessel internally of said rigid vessel and interiorly of said heat-insulating layer, said inner vessel having a bottom, side walls and a top made of a fluid-impervious metallic material, said inner vessel top having a defonnably, marginal portion in the area of juncture of said top and said side walls, said portion having a convex configuration arcuate in cross section bulging upwardly at said area of junction, said marginal portion bulging upwardly when said inner vessel is in an unloaded condition, the arcuate marginal portion extending peripherally of said top, said top having a central opening, a trunk in the top structure of said rigid vessel in communication with said opening, means securing to said top structure a marginal portion of said top of the inner vessel bounding said central opening, said heat-insulating layer including heat-insulating material over said top of the inner vessel deforming the top of said inner vessel inwardly in an unloaded condition of said inner vessel and causing deformation of said top to effect bulging of the top at said area of juncture with the side walls and said insulating material having a recess into which the upwardly bulging marginal portion extends and is received therein, whereby the first mentioned marginal portion will deform and bulge in the absence of a liquified gas load in the inner vessel and will straighten in cross section in response to temperature decreases and a loading of said inner vessel with liquified gas contained therein.

2. A receptacle for storing low-temperature liquified gas according to claim 1, in which said inner vessel is made of a thin metallic membrane.

3. A receptacle for storing low-temperature liquified gas according to claim 1, in which said heat-insulating layer material comprises rigid polyurethane.

4. A receptacle for storing low-temperature liquifled gas according to claim 1, in which said heat-insulating layer comprises a compression-resistant material. 

2. A receptacle for storing low-temperature liquified gas according to claim 1, in which said inner vessel is made of a thin metallic membrane.
 3. A receptacle for storing low-temperature liquified gas according to claim 1, in which said heat-insulating layer material comprises rigid polyurethane.
 4. A receptacle for storing low-temperature liquified gas according to claim 1, in which said heat-insulating layer comprises a compression-resistant material. 